The invention pertains to adaptation of cab high load bed covers used with pickup trucks to provide improved access to the load bed for loading/unloading and also to extend functions to new uses (where “cab high” is used to distinguish covers of approximately cab height, or greater, from load bed covers having a low profile, which are usually described as “tonneaus”). A major focus is upon achieving these benefits in a manner best accommodating processes broadly in use relative to conventional fixed mount cab high covers of the prior art (also referred to as “caps” and including covers having a height approximately matching vehicle cab height or greater, as distinct from low profile load bed covers usually described as tonneaus). Applicable US classifications include 296/100.1, 100.6 hinged load covers, 296/165 expansible or collapsible vehicle body, 296/176 expansible/collapsible from a first to a second configuration for camping. The disclosure describes a system which can be adapted for installation as part of a complete rear lifting load bed cover (similar to a lift-roof cover), or sold as a kit to be installed at a retail level. The system avoids or minimizes need for modification of the cap and ensures that aesthetic benefits are fully maintained. The application of an appropriately configured 4-bar hinging system, in combination with means for controlling associated functional geometric requirements independent of the installation process, overcomes key objections directed at lift-roof covers of the prior art.
(b) Description of Related Art
Enninga, U.S. Pat. No. 5,104,175, discloses an openable cover that is operable about an internally mounted, stationary pivot means disposed adjacent the inside top, forward end of the cover so that the cover may be rotated between open and closed positions with respect to the load bed. Limitations of the concept appear to include cost and complexity both in manufacturing and installation. A system is shown for attaching and rotating a conventional cab high load bed cover 17 to provide rear lift. The system employs hinged attachment of the cover to a frame comprising left and right side bases 21, 22 joined by a bridge 29 to create a frame fixedly attached to the vehicle load bed 13. Lever members 27, 37 are attached to the frame by pivots 25, 35. It appears that the cover 17 is attached to lever members 27, 67 and thereby pivots about pivots 25, 35. With this arrangement, attaching locations on the cover 17 must be used other than as provided by cover side wall mounting rails normally employed for fixed mounting of a cover to a vehicle load bed. This apparently requires mountings of some form to be added to the cover forward wall. Such modifications may adversely affect the future utility and value of the cover and are avoided in the present invention.
Medlin, U.S. Pat. No. 5,595,418, discloses a short/long arm system for pivotally attaching a camper shell (cab high load bed cover) to a vehicle load bed, allowing rear lift while keeping the cap upper forward edge clear of the vehicle cab. However, upper and lower arm pivots are disclosed as substantially one above the other on the cap forward wall (or adjacent to it on the side walls). These upper pivot locations appear to require a prohibitively heavy and costly form of arm construction in order to achieve levels of lateral rigidity which would provide stable positioning of the cap relative to a load bed when open and also probably present difficulty with respect to completing satisfactory installation. As in Lake U.S. Pat. No. 7,093,882, attachments at the cap forward wall appear to require techniques which prevent it from being conveniently adaptable to a variety of production caps.
Whereas Medlin discloses a large long upper arm above a large short lower arm, each arm pivoting from an upper attachment at, or adjacent to, the cap forward wall, the present invention employs relatively small short forward and long rearward arms, each pivoting from an upper attachment at, or close to, the horizontal mounting rail at the lower edge of each side wall. In Medlin, an upper arm upper pivot resides substantially vertically above a lower arm upper pivot on or proximate the cap forward wall (cap closed), whereas in the present invention arms are positioned so that the upper pivot of each arm lies substantially on, or close to, the same horizontal plane when closed, and at no time does one arm lie above the other. Medlin discloses lengths for upper and lower arms around 48 and 30 inches, respectively, which are 6 or more times longer than needed for arms in the present invention.
Technology of the prior art also includes a 4-bar hinging system used in forward hinged attachment of low profile molded unit covers (e.g. Leer model 700) to pickup load beds. However, 4-bar hinges of the prior art for low profile load bed cover applications, if applied to forward attachment of a cab high cover, provide insufficient rearward travel of the cap to maintain clearance between a truck cab and a load bed cap when raised.
Market testing of the lift-roof cover concept defined by Lake U.S. Pat. No. 7,093,882 revealed cost issues resulting from replacement of the cap forward wall with a hinged forward wall assembly and from associated complexities of addressing multiple applications of potential customer interest. Interest has been further limited by an associated loss of availability of forward window options demanded by many users of conventional caps. The present invention provides reductions in complexity of application relative to Lake U.S. Pat. No. 7,093,882 while giving up a small degree of functionality. The improvement in loading access is provided with use of readily available caps requiring minimal or no attachment modifications. The invention is simplified relative to Lake U.S. Pat. No. 7,093,882 by avoiding need for modification of the cover forward wall, thereby more easily maintaining functional robustness and supporting customer demand for pivoting, removable, or sliding forward window options.